A variety of containers and tubes are known in the art for collecting blood samples. Further, a variety of containers, for example Vacutainer® (Becton Dickinson) and methods are known in the art for centrifuging and separating whole blood into component layers including a cell layer, a gel layer and a plasma layer. However, a major drawback with the prior art methods is that the containers must be opened in order to analyze the plasma contained therein, thereby increasing the risk of infecting personnel with agents contained in the blood, and also increasing the risk of contaminating the blood during sampling. Thus, there is a need in the art for methods to analyze blood samples wherein the containers need not be opened to analyze plasma. Further, direct assaying of plasma following centrifugation is complicated by varied sample volumes that preclude direct assaying using a spectrophotometer. Also, direct assay of the plasma layer is often complicated due to the location of labels on the collection tubes, which may overlap the plasma layer. Thus, there is a need to overcome drawbacks in the art.
It is an object of the present invention to overcome drawbacks in the prior art.
The above object is met by a combination of the features of the main claims. The sub claims disclose further advantageous embodiments of the invention.